• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.1
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• pp.193-200
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• 2021

In this study, an analysis technique using static condensation is proposed for an efficient local nonlinear static analysis. The static condensation method is a model reduction method based on the degrees of freedom, and the analysis model is divided into a target part and a condensed part to be omitted. In this study, the nonlinear and linear parts were designated to the target and the omitted parts, respectively, and both the stiffness matrix and load vector corresponding to the linear part were condensed into the nonlinear part. After model condensation, the reduced model comprising the stiffness matrix and the load vector for the nonlinear part is constructed, and only this reduced model was updated through the Newton-Raphson iteration for an efficient nonlinear analysis. Finally, the efficiency and reliability of the proposed analysis technique were presented by applying it to various numerical examples.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.279-282
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• 2009

본 논문에서는 행렬응축기법 및 부구조기법을 이용하여 가변형 입체 복합 공간 구조물을 효율적으로 해석할 수 있는 해석기법을 제안하였다. 최근 구조공학의 발전과 더불어 다양한 사회적 경제적 요구에 의해 가변형 입체 복합 공간 구조물에 대한 연구가 진행되고 있다. 가변형 입체 복합 공간 구조물은 많은 구조부재가 필요 하며, 부재 수가 많아짐에 따라 각 절점이 가지는 자유도수가 크게 증가하여 초기 해석 과정에서 많은 시간이 요구된다. 또한 구조물이 변경되는 경우에는 변경되는 부분의 강성의 변화에 따라 전체 구조물의 강성이 변경되므로 이에 따른 전체 구조물의 재해석 과정이 필요하다. 이러한 점에서 구조물의 자유도수를 줄여주는 행렬응축기법과 반복적인 해석과정을 줄여주는 부구조기법은 가변형 입체 복합 공간구조물을 효율적으로 해석 할 수 있는 방법이 될 수 있다. 본 논문에서는 행렬응축기법과 부구조기법을 이용하여 가변형 입체 복합 공간 구조물을 효율적으로 해석할 수 있는 해석기법을 제안하고, 이를 토대로 구체적인 알고리즘을 작성하였다. 또한 알고리즘을 구체화시켜 가변형 입체 복합 공간 구조시스템에 적합한 구조해석 프로그램을 개발하여 예제 구조물에 대하여 구조해석을 수행하였으며, 구조해석 결과를 상용프로 그램의 구조해석 결과와 비교하여 해석기법에 대한 정확성 및 효율성을 검토하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.2
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• pp.193-202
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• 2001

현재 국내에서는 아파트 건물을 짓는데 벽과 바닥판으로만 이루어진 벽식 구조형식을 많이 사용하고 있다. 이러한 고층 아파트건물을 해석하기 위해서 ETABS나 MIDAS/BDS 같은 상용프로그램이 주로 사용되고 있다. ETABS는 해석상의 편의를 위하여 바다판을 강막으로 가정하여 모형화 하고 바닥판의 휨강성은 고려하지 않고 있다. 이러한 가정은 프레임 구조물을 해석할 때에는 합리적이라고 할 수 있다. 그러나 벽식 구조물은 바닥판의 휨강성이 전체 구조물의 횡방향 강성에 큰 영향을 미치므로 바닥판의 휨강성을 고려하지 않으면 전체 구조물의 강성을 과소평가하게 된다. 따라서 바닥판을 판요소로 세분하여 모형화 하는 것이 필요하다. 그러나 이때 많은 양의 해석 시간과 컴퓨터 메모리가 필요하게 된다. 따라서 본 연구에서는 부분구조법과 행렬응축기법을 사용하여 해석 시간과 컴퓨터 메모리의 사용을 줄이면서도 바닥판의 휨강성을 효율적으로 해석할 수 있는 해석 기법을 제안하였고 예제를 통하여 검증하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.3 s.73
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• pp.303-312
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• 2006

This paper presents the equivalent nodal load for the element stiffness which represents the influence of the stiffness change such as the addition of elements, the deletion of elements, and/or the partial change of element stiffness. The reanalysis of structure using the equivalent load improves the efficiency very much because the inverse of the structural stiffness matrix, which needs a large amount of computation to calculate, is reused in the reanalysis. In this paper, the concept of the equivalent load for the element stiffness is described and some numerical examples are provided to verify it.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.2 s.54
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• pp.57-68
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• 2007

The mega frame system is becoming popular for the design and construction of skyscrapers because this system exhibits structural efficiency by allowing high rigidity of the structure while minimizing the amount of structural materials to be used. Since the mega frame system is usually adopted for super high-rise buildings, the comfort of occupants may be main concerns in the practical application of this system. For the enhancement of the serviceability of mega frame structures, a semi-active tuned mass damper (STMD) is developed in this study. To this end, a Magnetorheological (MR) damper is employed replacing passive damper as a semi-active damper to improve the control effect of a conventional TMD. Since a conventional finite element model of mega frame structures has significant numbers of DOFs, numerical simulation for investigation of control performances of a STMD is impossible by using the full-order model. Therefore, a reduced-order system using minimal DOFs, which can accurately represent the dynamic behavior of a mega frame structure, is proposed in this study through the matrix condensation technique To improve the efficiency of the matrix condensation technique, multi-level matrix condensation technique is proposed using the structural characteristics of mega frame structures. The efficiency and accuracy of the reduced-order control proposed in this study and the control performance of a STMD were verified using example structures.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.4
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• pp.439-450
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• 2003

Flat plate system has been adopted in many buildings constructed recently because of the advantage of reduced floor heights to meet the economical and architectural demands. Structural engineers commonly use the effective beam width model(EBWM) in practical engineering for the analysis of flat plate structures. However, in many cases, when it is difficult to use the EBWM, it is necessary to use a refined finite element model for an accurate analysis. But it would take significant amount of computational time and memory if the entire building structure was subdivided with finer meshes. An efficient analytical method is proposed in this study to obtain accurate results in significantly reduced computational time. The proposed method employs super elements developed using the matrix condensation technique and fictitious beams are used in the development of super elements to enforce the compatibility at the interfaces of super elements. The stiffness degradation of flat plate system considered in the EBWM was taken into account by reducing the elastic modulus of floor slabs in this study. Static and dynamic analyses of example structures were performed and the efficiency and accuracy of the proposed method were verified by comparing the results with those of the refined finite element model and the EBWM.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.1
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• pp.79-88
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• 1997

Very stiff floor system in a residential-commercial building causes some problems in the numerical analysis procedure due to significant difference in stiffness with adjacent elements. Static analysis of structure with a stiff transfer-floor can be performed approximately in two steps for upper and lower parts for the structure. However, it is impossible to perform dynamic analysis in two steps with separate models. An efficient method for dynamic analysis of a structure with a right floor system is proposd in this study. The matrix condensation technique is employed to reduce the degree of freedom for upper and lower parts of the structure and a beam elements with rigid bodies at both ends are introduce to model the rigid floor system. Efficiency and accuracy of the proposed method are verified through analysis of several example structures.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.3 s.73
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• pp.283-293
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• 2006

Recently, various types of structural systems for skyscrapers are studied as the height and size of the building structures rapidly increase due to social and economical needs. The mega frame system among them, which is the structural system developed recently, is known as a suitable structural system for skyscrapers because this structural system has sufficient stiffness against the lateral forces by combination of mega members which consist of many columns and girders. Since the mega frame structure has significant numbers of elements and nodes, it takes tremendous times and computer memories to analyze and design the structures. Therefore, the exclusive structural analysis program for mega frame system is developed to reduce the efforts and time required for the analysis and design of mega frame structure. To this end, an efficient modelling technique using the characteristics of mega frame structures and an efficient analytical model, which uses a few DOFs selected by the user using the matrix condensation method, are developed in this study. Static and dynamic analyses are conducted using an example structure. The effectiveness and accuracy of the developed program we verified by the comparison between the results of the proposed method and the conventional method.

• Journal of Korean Association for Spatial Structures
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• v.11 no.3
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• pp.95-103
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• 2011

Among structural systems for complex-shaped tall buildings, diagrid system is widely used because of its structural efficiency and beauty of form. Recently, mega frame is favorably employed as a suitable structural system for skyscrapers because this structural system has sufficient stiffness against the lateral forces by combination of mega members which consist of many columns and girders. Diagrid mega frame system is expected to be promising structural system for future super tall buildings. However, it takes tremendous analysis times and engineer's efforts to predict the structural behavior of tall buildings applied with diagrid mega frame system because the diagrid mega frame structure has significant numbers of elements and nodes. Therefore, efficient analytical method for all buildings applied with diagrid mega frame system has been proposed in this study to reduce the efforts and time required for the analysis and design of diagrid mega frame structure. To this end, an efficient modelling technique using the characteristics of diagrid mega frame structures and an efficient analytical model using minimal DOFs by the matrix condensation method were proposed in this study. Based on the analysis of an example structure, the effectiveness and accuracy of the proposed method have been verified by the comparison between the results of the proposed method and the conventional method.